Abstract: In oilfield，some major problems have gradually emerged with the widespread employment of exploration technology，which can not be satisfactorily coped with through traditional physical-chemical techniques. Biological techniques have been widely used in crude oil production for their specific advantages. It is a current trend to deal with the problems in the oilfield ground system by using biological techniques. The aims of this paper are to expound the present status of biological techniques as defending and controlling the deleterious microbe，and developing biodemulsifier and bioflocculant so as to tackle some practical problems in actual oil production.